Oliver Burkeman: To sum up the Stoic perspective very simply: it's your beliefs about the world that cause distress, not the world itself.

Eric: And this leads to a very powerful technique for increasing happiness.

Oliver Burkeman: Yes. It's what the Stoics call, "the premeditation" — that there's actually a lot of peace of mind to be gained in thinking carefully and in detail and consciously about how badly things could go.

In most situations you're going to discover that your anxiety or your fears about those situations were exaggerated. It's so tempting to respond to anxiety and worry with reassurance, whether it's in ourselves or our kids or our friends. Somebody is really worried about the future. You want to try to convince them that it's all going to be okay. But of course the problem is that it reinforces the belief that if things weren't okay that would be a catastrophe.

Why thinking positive fails

Oliver Burkeman: There's one specific problem that keeps cropping up again and again, and that is this idea that when you try to control your thoughts or emotions with the will, consciously, it often ends up backfiring and bringing about the exact opposite. And research shows that same pattern occurring over and over; people who try not to feel grief after bereavement take longer to recover from grief. There's a great one about how people who are told not to feel aroused by looking at erotic pictures by skin conductivity measurements are shown to become more aroused than people who weren't given that instruction. People with low self-esteem feel worse when they repeat things like "I'm a lovable person" to themselves because doing that provokes them to generate counter arguments.

How to set goals that work

Oliver Burkeman: For a long time there's been an absolutely unquestioned dogma that having clear and ambitious goals is always a fantastic thing. I don't think that that is absolutely wrong in all cases but there's this huge shadow side to goal setting. There's a lot of evidence now that shows they can actually be demotivating. Goals can tempt people to cut ethical corners and to cheat when they are too rigidly focused on those goals.

The best thing to do is to set process goals rather than outcome goals. Stop telling yourself you're going to write the great American novel, and tell yourself you're going to do 500 words a day. Step back from focusing on the outcome and focus on process.

Oliver Burkeman: Eckart Tolle, who I interviewed for the book, has this great question: "Do you have a problem right now?" It's a very powerful thing to ask yourself, because the answer is almost always no. Our problems are almost always things that you imagine coming down the pike or things that happened in the past.